Immunotherapy of lung cancer has not been attempted to date primarily due to the lock of well defined lung tumor antigens. Project 3 deals with a candidate tumor antigen, cyclin B1. The hypothesis which we propose to test is that cyclin B1 expression is deregulated in multiple human lung tumors which leads to its accumulation in the cytoplasm where it is subject to degradation by proteasomes. This process provides greatly increased density of cyclin B1 peptides in HLA class I molecules on the surface of tumor cells, compared to normal cells, and leads to their recognition by the immune system as tumor antigens. Our aims are to document different mechanisms that underlie changes in cyclin B1 expression in lung tumor cells vs. normal cells, and to explore its utility as a target molecule of anti-tumor immune responses elicited in lung cancer patients by vaccination with selected cyclin B1 peptides. Specific Aim 1. will analyze deregulated expression of cyclin B1 in lung tumor cells vs. premalignant and normal cells to determine how general it is, when is it first seen in the process of malignant transformation, and the underlying molecular mechanisms (mutation, gene amplification, RNA and/or protein stability). Specific Aim 2, will use recombinant cyclin B1 protein (normal or mutated, as determined in Specific Aim 1) to evaluate its potential to elicit not only CTL responses but also helper T cell responses. In vitro priming will be employed using dendritic cells loaded with the whole protein or individual peptides, to generate T cells specific for this antigen and identify the whole repertoire of cyclin B1 peptides stimulatory to both CD8+ and CD4+ T cells. Specific Aim 3. will test cyclin B1 protein and peptide specific CTL generated in vitro on antigen-loaded dendritic c4ells, for their ability to destroy tumor cells but spare normal epithelial cells. We will employ our newest in vitro co-culture model of human lung cancer and select peptides that prime T cells that can specific target tumor cells and spare normal epithelial cells that surround them. Specific Aim 4. will be a phase I clinical trial in which lung cancer patients post surgery will be vaccinated with autologous dendritic cells loaded with a mixture of CD8 and CD4 stimulatory cyclin B1 peptides determined in Specific Aims 2 and 3 to be able to elicit tumor-specific T cells.